Abstract: Objective To understand the relationship of anxiety and depression with social behav?ior of young men who have sex with men（YMSM）.Methods A snowball sampling method was used to re?cruit YMSM aged 15-24 years in Mianyang City，Sichuan Province，to perform social behavior investiga?tion and serological testing. Self?rating anxiety scale（SAS）and self?rating depression scale（SDS）were ap?plied to measure anxiety and depression symptoms. Anxiety and depression symptoms and social behavior were analyzed with univariate analysis by Chi?square test and multivariate analysis by unconditional logis?tic regression. Results A total of 356 and 355 YMSM were separately determined by SAS and SDS，with a median age of 21 years. Of all the participants，62.08% had educational level of college or above， 68.54% were students or office clerks，and 55.06% had household registers in Mianyang. Total average score of SAS and SDS standard score were（42.96 ± 10.81）and（45.63 ± 12.40），and the detection rates of anxiety and depression symptoms were 23.60% and 33.24%，respectively. There was no significant dif?ference in the positive rate of HIV infection between groups with and without anxiety and depression symp?toms（P＞0.05），but the significant difference in syphilis infection rates was observed between groups with and without depression symptoms（P＜0.05）. Multivariate logistic regression showed that compared with insertive YMSM，the MSM with both receptive and insertive anal sex were more likely to detect anxi?ety（OR＝3.524）；suicidal thought and sexual abuse experience were the promoting factors of anxiety symptoms（OR＝2.782，14.013）；open sexual orientation was a protective factor（OR＝0.222）；the MSM with both receptive and insertive anal sex were more likely than insertive MSM and receptive MSM to have depression（OR＝3.916，2.309）；negative attitude of sex orientation and experience of sexual abuse were the promoting factors of depression symptoms（OR＝4.770，7.186）. Conclusion YMSM in Mianyang had high detection rates of anxiety and depression symptoms and poor mental health. Anxiety and depres?sive symptoms were associated with social behavior，and psychological intervention should be carried out.